My turn trying making dust storms:
By editing the snow fall texture, I could create... a swarm of rust mosquitoes?
I imagine you Ezer might be interested in the texture:
http://i.imgur.com/t2T5Pe4.png
Simply rename it to "snow.png" and toss it into the environment folder.
I was thinking the lower part of the skybox could become rust red all the way to the skyline, which would be a well pronounced feature when on high altitude locations. I didn't think about a volumetric fog effect of some sort though, but it would certainly be a really cool effect.
I'm not sure how such an effect could be done, but in theory it shouldn't be more complicated than how regular Minecraft clouds functions, but multi-layered and using a color matching the dust storm. In between this layer of clouds could be the transition zone for the actual fog.